The present invention relates generally communications systems, and more particularly to a stratospheric platform communications system having a platform antenna with adjustable boresight angles.
Communication satellites, such as geosynchronous earth orbit (GEO) satellite systems, have become commonplace for use in many types of communication services, i.e., data transfer, voice communications, television spot beam coverage, and other data transfer applications. As such satellites transmit and receive signals in predetermined configurations, i.e. bent pipe, or spot array, to focus signals in a desired geographic location on the Earth.
A stratospheric platform system employs airships, solar electric airplanes, or hydrogen powered electric airplanes, flying in the stratosphere. A stratospheric platform is located much closer to the Earth in comparison to a GEO satellite. A stratospheric platform can be viewed as an extra low-orbit GEO system if the stratospheric platform can maintain very tight station keeping standards.
Resources are scarce for over-the-air transmission. Therefore, various multiple-access schemes are used to provide a greater number of communication signals within an allocated communication band spectrum. Such multiple access schemes include code division multiple access (CDMA), time division multiple access (TDMA), frequency division multiple access (FDMA), or a combination of these schemes. Further, to prevent interference, the schemes may operate at different frequencies.
A frequency spectrum is assigned to direct broadcasting satellite (DBS) systems that are placed in GEO orbit. The DBS orbit slots have nine degrees or larger separation angels between two nearest DBS satellite locations. Currently there are eight GEO positions allocated to American DBS which are located at 175 W, 166 W, 157 W, 148 W, 119 W, 110 W, 101 W, and 61.5 W.
There is a need for a method and system that efficiently uses the resources available in a stratospheric platform system and that can adjust the capacity of a coverage area based on the use distribution in the coverage area.
It is an object of the present invention to efficiently use the frequency spectrum available for a stratospheric platform system. It is another object of the present invention to adjust the capacity of a coverage area. It is yet another object of the present invention to adjust the capacity of the coverage area based on a use distribution for the coverage area.
It is a further object of the present invention to adjust the stratospheric platform such that it is in a position that is most desirable for communicating. It is still a further object of the present invention to avoid interference with other wireless communication systems.
The present invention enables available resources to be used in the most efficient manner. The stratospheric platforms can operate at the same frequency spectrum as the DBF without interference from one another. In carrying out the above objects, the present invention provides a stratospheric platform system architecture with adjustable platform payload antenna boresight angles. The boresight angles are fine tuned to angle the antennas such that they benefit the communication system, effectively design a coverage capacity for a coverage area, and provide a system that may share a frequency spectrum with direct broadcasting GEO satellite systems.
These and other features of the present invention will be better understood with regard to the following description, appended claims, and accompanying drawings.